Title :
Temperature dependence of the magnetization of ultrafine particles of nickel
Author :
Li, Hua ; Gong, Wei ; Liu, Shuqing ; Shi, Guoshun
Author_Institution :
Inst. of Phys., Chinese Acad. of Sci., Beijing, China
fDate :
9/1/1992 12:00:00 AM
Abstract :
Partially oxidized Ni ultrafine particles were prepared by the gas evaporation method, and the magnetization of the particles has been measured between 1.5 and 250 K in applied fields up to 15 kOe. The results are well described by spin-wave theory (SW) and Stoner excitement (SE) above a characteristic temperature Ts which depends on the sizes of particles. Discrepancy of the data from SW and SE below Ts was associated with the superparamagnetism of antiferromagnetic NiO particles on the surface of ferromagnetic Ni particles. For temperatures above Ts, the spin-wave constants B were found to be 2.83×10-6 K-3/2 and 2.60×10-6 K-3/2 for particles with average diameters of 100 Å and 220 Å, respectively
Keywords :
ferromagnetic properties of substances; magnetic properties of fine particles; magnetisation; nickel; oxidation; particle size; spin waves; superparamagnetism; 1.5 to 250 K; Ni ultrafine particles; Stoner excitement; antiferromagnetic NiO particles; characteristic temperature; ferromagnetic particles; gas evaporation; magnetization; partial oxidation; spin-wave constants; spin-wave theory; superparamagnetism; temperature dependence; Kelvin; Magnetic field measurement; Magnetic materials; Magnetization; Nickel; Particle measurements; Physics; Temperature dependence; X-ray diffraction; X-ray imaging;
Journal_Title :
Magnetics, IEEE Transactions on
